Optimising the effectiveness of night purge

June 1, 2022

A ‘Night Purge' is an energy efficiency strategy designed to remove the built-up warm air from within a building and seeks to take advantage of cooler nighttime fresh air to reduce the demand on energy-intensive mechanical cooling systems. During the day, large buildings like shopping centers and offices will absorb heat from occupants, equipment, and the sun.

When evening temperatures drop, the night purge opens the building envelope, allowing cool air to enter and stored heat to dissipate. CIM’s PEAK Platform constantly monitors the HVAC  equipment required for night purge, as well as indoor and outdoor temperatures, and can identify inefficiencies in its operation.


As part of CIM’s continuous monitoring of a retail center in Western Australia, a night purge strategy was flagged as requiring attention. The night purge activity was scheduled to run in the building for two hours each day between 4am and 6am. Trend data captured by CIM confirmed that the return air temperature would typically see reductions only in the first hour of night purge, with the second hour of operation doing little more than circulating the air, with no additional cooling benefit. This resulted in unnecessary equipment operation and higher energy usage.


An Action was raised in the PEAK Platform and the Facilities Manager was notified with a recommendation to reduce the night cooling from two hours to one. The one hour was to take place during the coldest time of the day at the site (between 5am and 6am).          


The PEAK Action was promptly initiated. This immediately maximized the effectiveness of the daily night cooling activity, thereby optimizing the site’s energy consumption during this period, as a greater ventilation effect was enabled in half the time. This is a great example of an improvement opportunity that would have been difficult to identify without the real-time insights provided by the PEAK Platform.